JP2016191744A - Refractive index distribution type liquid crystal optical device and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refractive index distribution type liquid crystal optical device having high display quality, and to provide an image display device.SOLUTION: A refractive index distribution type liquid crystal optical device comprises: an optical element 101; and a control section. The optical element comprises: a first substrate 10 having a principal surface; a second substrate 20; a liquid crystal layer 30 provided between the principal surface of the first substrate and the second substrate; a plurality of first electrodes 11 provided between the principal surface of the first substrate and the liquid crystal layer and a plurality of second electrodes 12 provided among the plurality of first electrodes; and plural pairs of third electrodes 13 and plural pairs of fourth electrodes 14 provided between the second substrate and the liquid crystal layer. A pair of third electrodes is provided between a pair of fourth electrodes. When the fourth electrodes are projected on the principal surface, the fourth electrodes overlap with first mid-points of widths of the first electrodes in a first direction. When the plurality of second electrodes and the plural pairs of third electrodes are projected on the principal surface, each of the pair of the third electrodes overlaps with each of a pair of end portions possessed by one second electrode. The control section applies a voltage to each of the electrodes.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a gradient index liquid crystal optical device and an image display device.

There is known a liquid crystal optical device that utilizes the birefringence of liquid crystal molecules to change the refractive index distribution in response to application of a voltage. In addition, there is an image display device capable of displaying a stereoscopic image by combining the liquid crystal optical device and a display element.

In this image display device, by changing the refractive index distribution of the liquid crystal optical device, the image displayed on the display element is directly incident on the observer's eye, or a plurality of parallax images are incident on the observer's eye. You can make it. That is, this image display device can switch between two-dimensional display and three-dimensional image display. In addition, a technique for changing the light path using the optical principle of the Fresnel zone plate is also known. In such a display device, high display quality is required.

JP 2012-137762 A JP 2014-81534 A

An object of the present invention is to provide a refractive index distribution type liquid crystal optical device and an image display device with high display quality.

A gradient index liquid crystal optical device according to an embodiment includes a first substrate having a main surface, a second substrate,
A liquid crystal layer provided between the main surface of the first substrate and the second substrate; and a first liquid crystal layer provided between the main surface of the first substrate and the liquid crystal layer and parallel to the main surface. A plurality of firsts arranged in a direction
An electrode, provided between the main surface of the one substrate and the liquid crystal layer, disposed between the plurality of first electrodes, each provided between a pair of end portions and the pair of end portions. A plurality of second electrodes, a plurality of pairs of third electrodes provided between the second substrate and the liquid crystal layer, and provided between the second substrate and the liquid crystal layer. The plurality of pairs of thirds in the first direction.
An optical element comprising a plurality of pairs of fourth electrodes aligned with the electrodes; a first voltage applied to the plurality of first electrodes; a second voltage applied to the plurality of second electrodes; A control unit that applies a third voltage to three electrodes and applies a fourth voltage to the plurality of pairs of fourth electrodes, and the pair of third electrodes is provided between the pair of fourth electrodes, When the fourth electrode is projected onto the main surface, the fourth electrode overlaps a first midpoint of the width of the first electrode in the first direction, and the plurality of second electrodes
When the electrode and the plurality of pairs of third electrodes are projected onto the main surface, each of the pair of third electrodes overlaps each of the pair of end portions of one of the second electrodes, and the first voltage V1 The second voltage V2, the third voltage V3, and the fourth voltage V4 are:

Are in a relationship.

1A is a schematic cross-sectional view showing a gradient index liquid crystal optical device according to a first embodiment, and FIG. 1 is a schematic cross-sectional view showing an image display device according to a first embodiment. FIG. 3A is a schematic diagram showing the potential distribution of the gradient index liquid crystal optical device according to Reference Example 1, and FIG. 3B shows the electrodes of the gradient index liquid crystal optical device according to Reference Example 1. FIG. 4A is a schematic diagram showing the potential distribution of the gradient index liquid crystal optical device according to Reference Example 2, and FIG. 4B shows the electrodes of the gradient index liquid crystal optical device according to Reference Example 2. FIG. It is a schematic diagram which shows refractive index distribution with the refractive index distribution type liquid crystal optical device which concerns on the reference example 1 and the reference example 2. FIG. It is typical sectional drawing which shows the image display apparatus which concerns on 2nd Embodiment, and its partial enlarged view. It is typical sectional drawing which shows the image display apparatus which concerns on 3rd Embodiment. It is a typical perspective view which shows each electrode which concerns on 3rd Embodiment. It is a typical sectional view showing an image display device concerning a 4th embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between the parts, and the like are not necessarily the same as actual ones. Further, even when the same part is represented, the dimensions and ratios may be represented differently depending on the drawings.
Note that, in the present specification and each drawing, the same elements as those described above with reference to the previous drawings are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

(First embodiment)
FIG. 1A shows a gradient index liquid crystal optical device (liquid crystal optical device) 11 according to the first embodiment.
2 is a schematic cross-sectional view illustrating the configuration of 1. FIG. FIG.1 (b) is the elements on larger scale of Fig.1 (a). FIG. 2 is a schematic cross-sectional view showing the image display apparatus according to the first embodiment. The image display device 211 according to the present embodiment includes a liquid crystal optical device 111, a display element 80, and a display driving unit 87.

The liquid crystal optical device 111 includes a liquid crystal optical element 101 including a first substrate unit 10u, a second substrate unit 20u, and a liquid crystal layer 30, and a control unit 77.

 The liquid crystal layer 30 is provided between the first substrate unit 10u and the second substrate unit 20u.

The liquid crystal optical element 101 has a first state in which the optical path of incident light is changed and a second state in which the optical path of incident light is not substantially changed. That is, in the first state, the liquid crystal layer 30 has a refractive index distribution 31.
The second state is a state where the refractive index of the liquid crystal layer 30 is uniform. When light enters the liquid crystal optical element 101 in the first state, the image display device 211 provides, for example, three-dimensional display. In addition, when light enters the liquid crystal optical element 101 in the second state, the image display device 211 provides, for example, two-dimensional image display. The first state and the second state are switched when the state of the liquid crystal layer 30 is changed by the control unit 77.

The first substrate unit 10u includes a first substrate 10, a plurality of first electrodes 11, and a plurality of second electrodes 12. The first substrate 10 has a first main surface 10a. A plurality of first electrodes 11 and a plurality of second electrodes
The electrode 12 is provided between the first major surface 10 a of the first substrate 10 and the liquid crystal layer 30. The plurality of first electrodes 11 are arranged in a first direction parallel to the first major surface 10a. The plurality of second electrodes 12 are
They are arranged in a first direction parallel to the first major surface 10a. Each of the plurality of second electrodes 12 is disposed between the plurality of first electrodes.

The first direction is the X direction. A second direction perpendicular to the first major surface 10a is taken as a Z direction. A direction perpendicular to the X direction and the Z direction is taken as a Y direction. The XY plane is parallel to the first major surface 10a.

Each of the multiple first electrodes 11 extends, for example, in the Y direction parallel to the first major surface 10a and perpendicular to the first direction. Each of the multiple second electrodes 12 extends, for example, in the Y direction.

The second substrate unit 20 u includes the second substrate 20, the third electrode 13, and the fourth electrode 14. The second substrate 20 has a second main surface 20a facing the first main surface 10a. In this specification,
The state of being opposed includes not only the state of directly facing each other but also the state of facing each other with another element inserted therebetween. The plurality of pairs of third electrodes 13 are provided between the second major surface 20 a of the second substrate 20 and the liquid crystal layer 30. The plurality of pairs of third electrodes 13 are arranged in the first direction. Multiple pairs of third electrodes 1
For example, 3 extends in the Y direction.

The plurality of pairs of fourth electrodes 14 are provided between the second major surface 20 a of the second substrate 20 and the liquid crystal layer 30. The plurality of pairs of third electrodes 13 are arranged in the X direction. The multiple pairs of third electrodes 13 extend, for example, in the Y direction. The fourth electrode 14 is aligned with a plurality of pairs of third electrodes 13 in the X direction. The pair of third electrodes 13 is provided between the pair of fourth electrodes 14. The multiple pairs of fourth electrodes 14 extend in the Y direction, for example.

 Each of the first substrate unit 10u and the second substrate unit 20u may have an alignment film.

 The liquid crystal layer 30 is provided between the first substrate 10 and the second substrate 20.

The first substrate 10, the second substrate 20, the first electrode 11, the second electrode 12, the third electrode 13, and the fourth electrode 14 are light transmissive, for example, transparent.

For the first substrate 10 and the second substrate 20, for example, a transparent material such as glass or resin is used. The first substrate 10 and the second substrate 20 are, for example, plate-shaped or sheet-shaped. The thickness of the first substrate 10 and the second substrate 20 is, for example, 50 micrometers (μm) or more, 200
0 μm or less. However, the thickness is arbitrary.

The first electrode 11, the second electrode 12, and the third electrode 13 are, for example, indium (In), tin (
It includes an oxide containing at least one (one kind) element selected from the group consisting of Sn), zinc (Zn), and titanium (Ti). These electrodes include, for example, indium titanium oxide (IT
O) is used. For example, indium oxide (In ₂ O ₃ ) and tin oxide (SnO ₃ )
At least one of the above may be used. The thickness of these electrodes is, for example, not less than 100 nanometers (nm) and not more than 350 nm. The thickness of these electrodes is, for example, not less than about 150 nm and not more than 250 nm. The thickness of these electrodes is set to a thickness that provides a high transmittance for visible light, for example.

The pitch of the first electrodes 11 (the distance between the centers of the first electrodes 11 closest to each other in the X direction) is, for example, 10 μm or more and 1000 μm or less. This pitch is arbitrarily set. The distance between the first electrode 11 and the second electrode 12 adjacent thereto is 5 μm or more and 20 μm or less.

The width W1 along the first direction of the first electrode 11 is, for example, not less than 5 μm and not more than 300 μm. The width W2 of the second electrode 12 is, for example, not less than 5 μm and not more than 300 μm. The width W3 of the third electrode 13 is, for example, not less than 5 μm and not more than 30 μm. The width W2 of the second electrode 12 is larger than the width W3 of the third electrode 13, for example.

The liquid crystal layer 30 includes a liquid crystal material. As the liquid crystal material, for example, nematic liquid crystal (nematic phase at the use temperature of the liquid crystal optical device 111) is used. The liquid crystal material has a positive dielectric anisotropy or a negative dielectric anisotropy. In the case of positive dielectric anisotropy, the initial alignment of liquid crystals in the liquid crystal layer 30 (alignment when no voltage is applied to the liquid crystal layer 30) is, for example, substantially horizontal alignment. In the case of negative dielectric anisotropy, the initial alignment of the liquid crystal in the liquid crystal layer 30 is substantially vertical alignment.

In this specification, in horizontal alignment, a director of liquid crystal (a major axis of liquid crystal molecules) and X
The angle (pretilt angle) with respect to the −Y plane is 0 ° or more and 30 ° or less. In the vertical alignment, for example, the pretilt angle is not less than 60 ° and not more than 90 °. In at least one of the initial arrangement and the arrangement at the time of voltage application, the director has a component parallel to the X direction.

Hereinafter, the case where the dielectric anisotropy of the liquid crystal included in the liquid crystal layer 30 is positive and the initial alignment is substantially horizontal alignment will be described.

For a substantially horizontal orientation, in the initial alignment, the director is substantially parallel to the X direction. For example, when the director is projected onto the XY plane, the angle formed by the director and the X direction is 15 degrees or less. For example, the alignment direction of the liquid crystal in the vicinity of the second substrate unit 20u is antiparallel to the alignment direction of the liquid crystal in the vicinity of the first substrate unit 10u. That is, the initial orientation is not a splay arrangement.

The first substrate unit 10u may further include an alignment film (not shown). First substrate unit 10u
May further include an alignment film (not shown). For example, polyimide is used for these alignment films.

The control unit 77 controls the voltages of the first electrode 11, the second electrode 12, the third electrode 13, and the fourth electrode 14. The controller 77 can switch between the first state and the second state of the liquid crystal layer 30. The control unit 77 includes a plurality of first electrodes 11, a plurality of second electrodes 12, and a plurality of pairs of third electrodes 13.
Are electrically connected to the plurality of pairs of fourth electrodes 14. The control unit 77 includes the first electrode 11 and the second electrode
A voltage is applied between each of the electrode 12, the third electrode 13, and the fourth electrode 14 and the reference ground. The control unit 77 applies the first voltage V <b> 1 to the plurality of first electrodes 11, and the plurality of second electrodes 12.
The second voltage V2 is applied to the plurality of pairs of third electrodes 13, the third voltage V3 is applied to the plurality of pairs of third electrodes 13, and the plurality of pairs of fourth electrodes
A fourth voltage V4 is applied to the electrode 14.

In the first state, the control unit 77 changes the alignment of the liquid crystal in the liquid crystal layer 30 to form a refractive index distribution 31 in the liquid crystal layer 30. FIG. 1 schematically illustrates the refractive index distribution 31. The liquid crystal layer 30 in the first state will be described below.

One of the plurality of first electrodes 11 is a first electrode 11A, another one of the plurality of first electrodes 11 is a first electrode 11B, and another one of the plurality of first electrodes 11 is a first electrode 11C. And 1st electrode 1
The first electrode 11B is disposed between 1A and the first electrode 11C. In the following, the first electrode 11A
˜11C may be collectively referred to as the first electrode 11.

That is, in one cross section parallel to the XZ plane of the liquid crystal optical element 101, the first electrode 11A
The distance along the X direction between the center in the X direction and the center in the X direction of the first electrode 11B is between the center in the X direction of the first electrode 11B and the center in the X direction of the first electrode 11C. It is substantially equal to the distance along the X direction.

The liquid crystal layer 30 has a plurality of lens portions in the first state. Multiple lens parts
A first lens portion 71 and a second lens portion 72 are provided. The first lens portion 71 includes the liquid crystal layer 3
When 0 is projected onto a plane (XY plane) parallel to the first major surface 10a, the first electrode 11
This is a portion between the center line parallel to the Y direction of A and the center line parallel to the Y direction of the first electrode 11B. The second lens portion 72 is configured so that the liquid crystal layer 30 is a plane parallel to the first major surface 10a (XY).
This is a portion between the center line of the first electrode 11B and the center line of the first electrode 11C when projected onto a plane. The center lines parallel to the Y direction of the first electrodes 11A to 11C are the first electrodes 11A to 1A.
1C is a line passing through the center of the width in the first direction. The refractive index distribution 31 in the second lens portion 72 is substantially the same as the refractive index distribution 31 in the first lens portion 71. Hereinafter, the refractive index distribution 31 in the first lens portion 71 will be described.

A plane parallel to the YZ plane passing through the midpoint of the line connecting the center of the first electrode 11A in the X direction and the center of the first electrode 11 in the X direction when projected onto the XY plane. Center plane 59
And The center plane 59 is, for example, a plane that passes through the center of the second electrode in the X direction and is parallel to the YZ plane. The refractive index distribution 31 of the first lens portion 71 is plane symmetric with respect to the center plane 59. In order to obtain desired optical characteristics or due to variations in manufacturing conditions, the refractive index distribution 31 of the first lens portion 71 may be asymmetric with respect to the center plane 59. In the following, the first lens portion 7
The refractive index distribution 31 of 1 is symmetric with respect to the center plane 59.

Of the first lens portion 71, the center surface 59 and one first electrode 11 (for example, the first electrode 11B).
The part between is explained.

In the first state, the liquid crystal layer 30 includes a first portion 30a, a second portion 30b, and a third portion 30c that are arranged along the + X direction from the center surface 59 toward the end of the first electrode 11. The first portion 30a is a portion where the refractive index n decreases in the + X direction. The second portion 30b is a portion where the refractive index n increases in the + X direction. The third portion 30c is a portion where the refractive index n decreases in the + X direction.

The liquid crystal optical element 101 has, for example, Fresnel lens optical characteristics. Refractive index distribution 31
Has a shape corresponding to the lens thickness distribution in the Fresnel lens, for example. The liquid crystal optical element 101 includes a liquid crystal GRIN lens (Gradient Index len) whose refractive index n varies in the plane.
s). Since the liquid crystal optical element 101 has the optical characteristics of a Fresnel lens,
It is thin and the response speed of the liquid crystal layer 30 is fast.

The liquid crystal optical element 101 in the present embodiment functions as, for example, a cylindrical lens that is an example of a Fresnel lens. Each Fresnel lens has a curvature in the X direction of FIG. 1, and the direction of incident light can be controlled. On the other hand, since there is no curvature in the Y direction, the direction of incident light slightly changes so as to pass through the parallel plane glass. The liquid crystal optical element 101 is
For example, you may function as a fly array lens etc. which are examples of a Fresnel lens.

  The display element 80 will be described below.

As the display element 80, for example, a liquid crystal display element, an organic EL display element, a plasma display, or the like can be used. The embodiment is not limited to this, and any display device can be used for the display element 80. The display element 80 is stacked with the liquid crystal optical element 101. In this specification, the state of being stacked includes not only the state of being stacked in direct contact but also the state of being stacked with other elements inserted therebetween.

The display element 80 includes a plurality of element image areas. The plurality of element image areas include a first element image area 81 and a second element image area 82. One element image area corresponds to one lens portion. For example, the first element image region 81 faces the second lens portion 72.

In the present embodiment, a configuration is shown in which the positions where the element image region and the lens portion are projected onto the XY plane coincide with each other. For example, the deviation between the center of the element image area and the center of the lens portion may increase from the center of the display element 80 toward the outer edge.

A signal including video information is supplied from the display driver 87 to the display element 80. The display element 80 generates light that is modulated based on the signal. The display element 80 can emit light including a plurality of parallax images, for example.

For example, the first element image region 81 includes first to Nth (N is an integer of 2 or more) main region parallax image display units P1 to Pn (n is the same integer as N) arranged in order in the X direction. Have. The second element image region 82 includes first to Nth adjacent region parallax image display units Q1 to Q arranged in order in the X direction.
n (n is the same integer as N).

In FIG. 1, a case where N is 5 is illustrated for easy understanding of the drawing.
N is arbitrary.

Each of the first to Nth main region parallax image display units P1 to Pn and the first to nth plurality of adjacent region parallax image display units Q1 to Qn includes, for example, a plurality of An image including parallax information is generated. The observer perceives, for example, a stereoscopic image by viewing a plurality of parallax images through a lens formed by the liquid crystal optical device 111.

In order to provide a high-quality stereoscopic image, it is ideal that the second portion 30b of the liquid crystal layer 30 is absent. That is, the refractive index n between the first portion 30a and the third portion 30c is the first major surface 1.
Ideally it increases perpendicular to 0a. However, for convenience of design, the second part 3
It is difficult to eliminate 0b.

When light from the display element 80 enters the second portion 30b of the liquid crystal layer 30, the light is guided in a direction that is not ideal for generating a parallax image. For example, stray light is generated. In this case, for example, crosstalk occurs, and the display quality of the image display device 211 is low. This phenomenon is more likely to occur as the width of the second portion 30b is wider.
A conventional first portion 30a and second portion 30b will be described with reference to FIG. The third
Description of the portion 30c is omitted. FIG. 3A is a schematic diagram showing a potential distribution of the gradient index liquid crystal optical device according to Reference Example 1 obtained by simulation, and FIG. 3B is a gradient index liquid crystal optical device according to Reference Example 1. It is a partial cross section enlarged view which shows this electrode. FIG. 3A corresponds to the cross section of FIG.

There is a sixth electrode 16 between the first substrate 10 and the liquid crystal layer 30. Second substrate 20 and liquid crystal layer 30
There is a pair of eighth electrodes 18 and a pair of seventh electrodes 17 provided between the pair of eighth electrodes. The sixth electrode 16 faces the pair of seventh electrodes 17 and the pair of eighth electrodes 18. In such a configuration, the potential difference between the sixth electrode 16 and the seventh electrode 17 is increased, and the sixth electrode 1
Ideally, the refractive index profile 32 is generated by reducing the potential difference between the sixth electrode 18 and the eighth electrode 18. A director of liquid crystal molecules is indicated by an ellipse 32.

Here, the voltage applied between the seventh electrode 17 and the sixth electrode 6 may be increased in order to make the change in the refractive index n in the second portion 30b steep and to narrow the width of the second portion 30b. Conceivable. However, according to the study by the present inventors, it has been found that a reverse tilt region is formed around the seventh electrode 17 in this case.

That is, as shown in FIG. 3A, the seventh electrode 17 and the eighth electrode 18 are close to each other.
The electric field generated by the sixth electrode 16 and the seventh electrode 17 spreads in the vicinity of the eighth electrode 18. Further, the electric field generated by the sixth electrode 26 and the eighth electrode 18 spreads outside. Therefore, the second
It is difficult to make the change of the refractive index n in the portion 30b steep. Also, as shown in the area 301, disclination may occur. FIG. 3A shows a case where 0 volt (V) is applied to the sixth electrode 16, 6 V is applied to the seventh electrode 17, and 0 V is applied to the eighth electrode 18.

The first portion 30a and the second portion 30b according to the present embodiment will be described with reference to FIG.
The description of the third portion 30c is omitted.

4A is a schematic diagram showing a potential distribution of the gradient index liquid crystal optical device according to Reference Example 2 obtained by simulation, and FIG. 4B is a gradient index liquid crystal optical device according to Reference Example 2. FIG. It is a partial cross section enlarged view which shows this electrode. FIG. 4A corresponds to the cross section of FIG. FIG. 4 shows a case where the fourth electrode 14 of the liquid crystal optical device shown in FIG. 1 is omitted. FIG. 5 is a schematic diagram showing a refractive index distribution with the refractive index distribution type liquid crystal optical device according to Reference Example 1 and Reference Example 2. FIG.
Corresponds to the cross sections of FIG. 3B and FIG. 4B, with the horizontal axis representing the X direction and the vertical axis representing the Y direction.

The potential difference between the second electrode 12 and the third electrode 13 is increased, and the first electrode 11 and the third electrode 13 are increased.
The refractive index distribution 33 can be generated by reducing the potential difference of. 1st electrode 1
By controlling the voltages of the first and second electrodes 12, the electric field generated in the first portion 30a and the electric field generated in the second portion 30b can be adjusted, so that the change in the refractive index n in the second portion 30b is made steep. can do. In addition, since it is not necessary to increase the potential difference between the second electrode 12 and the third electrode 13, the occurrence of disclination can be suppressed. FIG. 4A shows a case where 0 volt (V) is applied to the first electrode 11, -4V is applied to the second electrode 12, and + 2V is applied to the third electrode.

Thus, by forming two types of electrodes on the first substrate 10 side where the convex shape of the lens is formed, the liquid crystal optical element 101 that functions as an ideally shaped Fresnel lens can be obtained. Therefore, according to the present embodiment, it is possible to provide the liquid crystal optical device 111 and the image display device 211 with high display quality.

Each of the second electrodes 12 has a pair of end portions 12a and a central portion 12b provided between the pair of end portions 12a. The pair of third electrodes 13 opposes one second electrode 12. Multiple second
When the electrode 12 and the plurality of pairs of third electrodes 13 are projected onto the first main surface 10a, each of the pair of third electrodes 13 overlaps with each of the pair of end portions 12a of the one second electrode 12.

By facing the end 12a of the second electrode 1 and the third electrode 13, the valley of the refractive index distribution generated between the first portion 30a and the second portion 30b of the liquid crystal layer 30 can be deepened. That is, an ideal refractive index distribution can be obtained near the boundary between the first portion 30a and the second portion 30b. The width along the first direction of the end portion 12a of the second electrode 12 is, for example, not less than 10 μm and not more than 30 μm.

 Furthermore, the width W2 of the second electrode 12 is preferably equal to or greater than the thickness L1 of the liquid crystal layer 30.

When the width W2 of the second electrode 12 is narrow, the width of the second portion 30b is wide. The width of the second portion 30b becomes narrower as the width W2 of the second electrode 12 is wider. When the width W2 of the second electrode 12 is smaller than the thickness L1 of the liquid crystal layer, the width of the second portion 30b can be reduced.

When the width W <b> 2 of the second electrode 12 is shorter than the thickness L <b> 1 of the liquid crystal layer 30, the valley of the refractive index distribution generated by the electric field between the second electrode 12 and the third electrode 13 is shallow. The electric field generated by the second electrode 12 and the third electrode 13 spreads between the first electrode 11 and the third electrode 13. The second portion 30b is generated on the fourth electrode 14 side of the electric field, and the width of the second portion 30b is increased. On the other hand, when the width W2 of the second electrode 12 is longer than the thickness L1 of the liquid crystal layer 30, the valley of the refractive index distribution can be deepened, and the width of the second portion 30b can be made difficult to widen.

In the present embodiment, the width W2 along the first direction of one second electrode 12 is assumed to be constant. In addition, the width W3 along the first direction of one third electrode 12 is assumed to be constant. When the width along the first direction of one second electrode 12 is not constant, for example, an average value of the width is set as the width W2. When the width along the first direction of one third electrode 12 is not constant, for example, an average value of the width is set as a width W3.

In the present embodiment, it is assumed that the width W2 along the first direction of each of the plurality of second electrodes 12 is the same. In addition, the width W3 along the first direction of each of the plurality of pairs of third electrodes 13 is the same. When the width along the first direction of each of the plurality of second electrodes 12 is different, for example, an average value of the plurality of second electrodes 12 is set as a width W2. When the width along the first direction of each of the plurality of third electrodes 13 is different, for example, an average value of the plurality of third electrodes 13 is set as a width W3.

When the fourth electrode 14 is projected onto the first major surface 10a, the fourth electrode 14 overlaps the midpoint (first midpoint) M1 of the width of the first electrode 11 in the first direction. That is, a straight line passing through the first middle point M1 and perpendicular to the first major surface 10a passes through the fourth electrode 14.

In the first state, the control unit 77 applies a voltage to each electrode so that the first voltage V1, the second voltage V2, the third voltage V3, and the fourth voltage V4 satisfy the following relationship.

By increasing the potential difference between the second voltage V2 and the third voltage V3 as shown in Equation 3, the liquid crystal director can be started up, and the valley of the refractive index distribution between the first portion 30a and the second portion 30b can be increased. Is formed. By reducing the potential difference between the first electrode 11 and the third electrode 13, it is difficult for the liquid crystal director to rise, and a peak of refractive index is formed between the second portion 30b and the third portion 30c.

For example, the first voltage V1 is larger than the second voltage V2, the third voltage V3 is equal to or higher than the first voltage V1, and the first voltage V1 to the third voltage V3 can be set so as to satisfy Expression 3. .
The difference between the first voltage V1 and the third voltage V3 is preferably close to zero.

The end of the Fresnel lens has the lowest refractive index among the Fresnel lenses. By making the potential difference between the first electrode 11 and the fourth electrode 14 larger than the potential difference between the first electrode 11 and the third electrode 13 as shown in Expression 4, the third portion 30c has a refractive index profile that is close to ideal. be able to.
That is, when Expression 4 is satisfied, the third portion 30c has a lower refractive index as it is farther from the second portion 30b.

The length G1 along the X direction of the gap between the first electrode 11 and the second electrode 12 closest to the first electrode 11 is preferably not more than the thickness L1 of the liquid crystal layer 30 in the Z direction. When the first electrode 11 and the second electrode 12 are arranged in this manner, the width of the second portion 30b can be reduced.

A mechanism by which the refractive index distribution of the second portion 30b is formed will be described. First electrode 11 and second
When different voltages are applied between the electrodes 12, a plurality of equipotential lines extend in the Z direction from the gap between the first electrode 11 and the second electrode 12, and an electric field having a potential gradient in the X direction is generated. First electrode 11 and second
The smaller the gap between the electrodes 12, the higher the density of the plurality of equipotential lines. The plurality of equipotential lines extend from the first substrate 10 side to the second substrate 20 side while maintaining an interval. In this equipotential line range, the liquid crystal director rises along the Y direction. By narrowing the gap between the first electrode 11 and the second electrode 12, the width of the electric field generated by these potential differences can be narrowed, so that the rise of the liquid crystal director is made steep and the width of the second portion 30b is narrowed. be able to. The length G1 of the gap between the first electrode 11 and the second electrode is preferably as narrow as possible. For example, the gap G1 is made smaller than the thickness L1 of the liquid crystal layer 30. For example, this gap G1
Is preferably 20 μm or less.

In the present embodiment, the length G1 along the X direction of the gap between one first electrode 11 and one second electrode 12 closest to the first electrode 11 is assumed to be constant. When this length is not constant, for example, the average value of the length is set to G1. Moreover, when the lengths along the X direction of the intervals between the plurality of first electrodes 11 and the second electrodes 12 are different from each other, for example, an average value thereof is set as a length G1.

The thickness of the liquid crystal layer 30 is the distance between the first substrate unit 10u and the second substrate unit 20u. For example, when each of the first substrate unit 10 u and the second substrate unit 20 u has an alignment film, the distance between the alignment films is the thickness of the liquid crystal layer 30.

(Second Embodiment)
The same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. FIG. 6 shows the second
It is a typical sectional view showing the image display device concerning this embodiment, and its partial enlarged view. In the present embodiment, the liquid crystal optical device 112 of the image display device 212 includes the liquid crystal optical element 102. In the liquid crystal optical element 102, the second substrate unit 20 u further includes a fifth electrode 15.

The fifth electrode 15 is provided between the second substrate 20 and the liquid crystal layer 30. The fifth electrode 15 is provided between the third electrode 13 and the fourth electrode 14. A pair of fifth electrodes is provided between the pair of fourth electrodes 14.

The second middle point M2 of the line segment along the X direction connecting the first electrode 11 and the second electrode is located in the gap between the third electrode 13 and the fifth electrode 15 projected onto the first major surface 10a. .

The arrangement of the third electrode 13 and the fifth electrode 15 will be described. It is preferable that the second electrode 12 and the third electrode 13 have a strong coupling action in order to form the first portion 30a. For this purpose, it is preferable that the third electrode 13 hardly causes a coupling action with the first electrode 11. Accordingly, the third electrode 13 is disposed so as not to overlap the first middle point M1 when projected onto the first major surface 10a. That is, in the XZ plane, the third electrode 13 is provided on the side close to the central portion 12a of the second electrode 12 of a line passing through the first middle point M1 and parallel to the Z direction.

On the other hand, it is preferable that the first electrode and the fifth electrode 15 have a strong coupling action in order to form the second portion. For this purpose, the fifth electrode 15 is disposed so as not to overlap the first middle point M1 when projected onto the first major surface 10a. That is, in the XZ plane, the fifth electrode 15
Is provided on the side close to the first electrode 11 of a line passing through the first middle point M1 and parallel to the Z direction.

In the liquid crystal optical device 111 in which the fifth electrode 15 is not provided as in the first embodiment, an ideal refractive index distribution is formed in the liquid crystal layer 30 depending on the material of the liquid crystal layer 30 and the voltage value applied to each electrode. It may be difficult. Depending on the material of the liquid crystal layer 30, the refractive index distribution may be easily disturbed particularly in the second portion 30 b of the liquid crystal layer 30. However, when the fifth electrode 15 is provided, the potential distribution generated between the third electrode 13 and the fourth electrode 14 can be adjusted, so that a more ideal refractive index distribution 31 can be formed. .

Therefore, according to the present embodiment, it is possible to provide the liquid crystal optical device 112 and the image display device 212 with high display quality.

For example, the width W2 of the second electrode 12 along the X direction is equal to the width W5 of the fifth electrode 15 along the X direction.
Can be larger. For example, the width W3 of the third electrode 13 along the X direction can be equal to or less than the width W5 of the fifth electrode 15 along the X direction. The fifth electrode 15 is the first electrode 11.
A material similar to that of the fourth electrode 14 can be used. The width of the fifth electrode 15 is, for example, 10 μm
m to 30 μm. The gap between the third electrode 13 and the fifth electrode 15 is, for example, not less than 10 μm and not more than 20 μm. The gap between the fourth electrode 14 and the fifth electrode 15 is, for example, 20 μm or more and 70 μm.
m or less. The gap between the fourth electrode 14 and the fifth electrode 15 is set in accordance with an ideal refractive index distribution (curvature) in the third portion 30c. For example, the gap between the third electrode 13 and the fifth electrode is
Narrower is better.

  The controller 77 applies the fifth voltage V5 to the fifth electrode.

The first voltage V1, the second voltage V2, the third voltage V3, and the fifth voltage V5 preferably satisfy the following relationship.

The range on the second substrate 20 on which the third electrode 13 and the fifth electrode 15 are provided has a third voltage V
3 and the average voltage VA of the fifth voltage V5 can be considered applied. As shown in Equation 5, the liquid crystal director can be started up by increasing the potential difference between the second voltage V2 and the average voltage VA, and the valley of the refractive index distribution between the first portion 30a and the second portion 30b can be increased. Is formed. By reducing the potential difference between the first electrode 11 and the average voltage VA, it is difficult for the liquid crystal director to rise, and a peak of refractive index is formed between the second portion 30b and the third portion 30c.

For example, the first voltage V1 is lower than the second voltage V2, the average voltage VA is lower than the first voltage V1, and the respective voltage values can be set so as to satisfy Expression 5. Average voltage VA
The absolute value of the potential difference between the first voltage V2 and the second voltage V2 is preferably equal to or higher than the threshold voltage Vth of the liquid crystal layer 30.
The absolute value of the potential difference between the average voltage VA and the first voltage V1 is preferably equal to or lower than the threshold voltage Vth of the liquid crystal layer 30.

The first voltage V1, the second voltage V2, the third voltage V3, and the fifth voltage V5 preferably satisfy the following relationship in addition to Equation 5.

An electric field caused by the second voltage V2 and the third voltage V3 is generated between the second electrode 12 and a portion of the third electrode 13 close to the second electrode 12. In addition, an electric field is generated by the first voltage V1 and the fifth voltage V5 between the first electrode 11 and the portion of the fifth electrode 15 close to the first electrode 11. When Expression 6 is satisfied, a refractive index distribution closer to ideal can be obtained. The difference between the first voltage V1 and the fifth voltage V5 is preferably close to zero.

The first voltage V1, the second voltage V2, the third voltage V3, and the fifth voltage V5 preferably satisfy the following second relationship.

When each voltage is set in this manner, the potential relationship along the X direction on the first substrate unit 10u side and the second substrate unit 20u side is reversed. For example, the liquid crystal layer 30 is near the first substrate unit 10u.
The potential on the first electrode 11 side is higher than that on the second electrode 12 side, whereas the potential on the third electrode 13 side is higher than that on the fifth electrode 15 side in the vicinity of the second substrate portion 20u. Thus, the liquid crystal layer 30
A maximum value of the refractive index is easily formed between the second portion 30b and the third portion 30c. Therefore, it is possible to obtain a refractive index profile that is closer to the ideal.

(Third embodiment)
The same components as those in the second embodiment are denoted by the same reference numerals, and description thereof is omitted. FIG. 7 is a schematic cross-sectional view showing a gradient index liquid crystal optical device according to the third embodiment. In the present embodiment, the liquid crystal optical device 113 of the image display device 213 includes the liquid crystal optical element 103. In the liquid crystal optical element 103, the first substrate unit 10 u further includes a ninth electrode 19.

In the present embodiment, the second substrate unit 20u is the same as that in the second embodiment, but the fifth electrode 15 may not be provided.

The ninth electrode 19 is provided between the first substrate 10 and the liquid crystal layer 30. The ninth electrode 19 is
Provided between the first electrode 11 and the second electrode 12. The second electrode 12 is interposed between the pair of ninth electrodes 19.
Is provided. When the fifth electrode 15 is provided, at least a part of the fifth electrode 15 and at least a part of the ninth electrode 19 face each other. That is, when the fifth electrode 15 is projected onto the first major surface 10 a, it overlaps at least a part of the ninth electrode 19.

In the case where the ninth electrode 19 is provided, the potential distribution generated between the first electrode 11 and the second electrode 12 can be adjusted, so that a more ideal refractive index distribution 31 can be formed.

Therefore, according to the present embodiment, it is possible to provide the liquid crystal optical device 113 and the image display device 213 with high display quality.

In the present embodiment, each voltage preferably satisfies the following relationship.

When each voltage has such a relationship, the width of the second portion 30b can be reduced. Further, the refractive index of the third portion 30c can be lowered as the distance from the first portion 30a increases.

FIG. 8 is a schematic perspective view showing an example of each electrode according to the third embodiment. Adjacent first
The electrodes 11, the adjacent second electrodes 12, the adjacent third electrodes 13, the adjacent fourth electrodes 14, the adjacent fifth electrodes 15, and the adjacent ninth electrodes 19 are connected 414.
˜419.

A group of two connected first electrodes 11 are arranged in the Y direction. A group of two connected second electrodes 12 are arranged in the Y direction. A group of two connected fifth electrodes 15 are arranged in the Y direction. A group of two connected ninth electrodes 19 are arranged in the Y direction. On the other hand, the group of connected third electrodes 13 is arranged in the X direction. The group of connected fourth electrodes 14 is arranged in the X direction.

The controller 77 can give two types of voltage values to each of these electrodes. For example, the control unit 77 can apply the first high voltage V1H and the first low voltage V1L to the first electrode 11. For example, the controller 77 can apply the second high voltage V2H and the second low voltage V2L to the second electrode 12. For example, the control unit 77 can apply the third high voltage V3H and the third low voltage V3L to the third electrode 13. For example, the control unit 77 applies the fourth high voltage V4 to the fourth electrode 14.
H and the fourth low voltage V4L can be applied. For example, the control unit 77 can apply the fifth high voltage V5H and the fifth low voltage V5L to the fifth electrode 15. For example, the control unit 77
A ninth high voltage V9H and a ninth low voltage V9L can be applied to the electrode 19. By switching the voltage applied to each electrode by the control unit, the image display device performs a 3D display or a 2D display.
Display. That is, 3D display or 2D display can be performed in each of the first region R1 to the fourth region R4 arranged along one main surface parallel to the XY plane.

For example, in one region, the first electrode 11, the second electrode 12, the fifth electrode 15, and the ninth electrode 19 are set to a low voltage, the third electrode and the fourth electrode are set to a high voltage, If so, 3D display can be performed in this area. In this case, specifically, Equation 1
The relationship of 1 and 12 is established.

On the other hand, when the first electrode 11, the second electrode 12, the fifth electrode 15, and the ninth electrode 19 are set to a high voltage, and the third electrode and the fourth electrode are set to a high voltage, 2D display (first 2D display) is performed. It can be carried out. For example, the voltage of each electrode is set to satisfy the following relationship.

When the first electrode 11, the second electrode 12, the fifth electrode 15, and the ninth electrode 19 are set to a low voltage and the third electrode and the fourth electrode are set to a low voltage, 2D display (second 2D display) can be performed. it can. For example, the voltage of each electrode is set to satisfy the following relationship.

When the first electrode 11, the second electrode 12, the fifth electrode 15, and the ninth electrode 19 are set to a high voltage and the third electrode and the fourth electrode are set to a low voltage, 2D display (third 2D display) can be performed. it can. For example, the voltage of each electrode is set to satisfy the following relationship.

 In the case of 2D display, no refractive index distribution occurs in the liquid crystal layer 30.

(Fourth embodiment)
The same components as those in the third embodiment are denoted by the same reference numerals, and description thereof is omitted. FIG. 9 is a schematic cross-sectional view showing a gradient index liquid crystal optical device according to the fourth embodiment. In the present embodiment, the liquid crystal optical device 114 of the image display device 214 includes the liquid crystal optical element 104. In the liquid crystal optical element 104, the second substrate unit 20 u further includes a tenth electrode 310 and an eleventh electrode 311.

The tenth electrode 310 and the eleventh electrode 311 are provided between the first substrate 10 and the liquid crystal layer 30. The tenth electrode 310 is provided between the fourth electrode 14 and the fifth electrode 15. The eleventh electrode 311 is provided between the tenth electrode 310 and the fourth electrode 14. A pair of fourth electrodes 14
A pair of tenth electrode 310 and eleventh electrode 311 are provided between the two electrodes.

In the present embodiment, the refractive index profile 32 includes a first portion 32a that faces the central portion 12b of the second electrode 12, a fifth portion 32e that faces the fourth electrode 14, a first portion 32a, and a fifth portion. The second portion 32b positioned between the second portion 32b, the third portion 32c positioned between the second portion 32b and the fifth portion 32e, and the third portion 32c positioned between the third portion 32c and the fifth portion 32e. 4 parts 3
2d. The second portion 32b and the fourth portion 32d are portions where the refractive index decreases as the distance from the first portion 32a increases. The third portion 32c and the fifth portion 32e are portions where the refractive index increases as it is closer to the first portion 32a.

That is, in the first to third embodiments, a two-stage Fresnel lens is formed, but in the present embodiment, a three-stage Fresnel lens is formed.

When the tenth electrode 310 and the eleventh electrode 311 are provided, the number of peaks in the refractive index distribution can be increased by adjusting the potential distribution generated between the fourth electrode 14 and the fifth electrode 15. Accordingly, the function of a Fresnel lens having a large refractive power can be obtained.

Also in this embodiment, an ideal refractive index profile 32 can be formed. Therefore, according to the present embodiment, it is possible to provide the liquid crystal optical device 114 and the image display device 214 with high display quality.

In the present specification, “vertical” and “parallel” include not only strictly vertical and strictly parallel, but also include, for example, variations in the manufacturing process, and may be substantially vertical and substantially parallel. It ’s fine.

The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, a liquid crystal optical element included in the image display device, a first substrate unit, a second substrate unit, a liquid crystal layer, a first substrate, a second substrate, each electrode, an edge layer, a control unit,
As for the specific configuration of each element such as the display unit and the display driving unit, the present invention is similarly implemented by appropriately selecting from a well-known range by those skilled in the art, so long as the same effect can be obtained. It is included in the range.

Moreover, what combined any two or more elements of each specific example in the technically possible range is also included in the scope of the present invention as long as the gist of the present invention is included.

In addition, any image display device that can be implemented by a person skilled in the art based on the above-described image display device as an embodiment of the present invention also includes the scope of the present invention as long as it includes the gist of the present invention. Belonging to.

In addition, in the category of the idea of the present invention, those skilled in the art can conceive of various changes and modifications, and it is understood that these changes and modifications also belong to the scope of the present invention. .

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

10 ... 1st board | substrate,
10a ... 1st main surface,
10u ... 1st substrate part,
11 ... 1st electrode,
12 ... second electrode,
12a ... the end of the second electrode,
12b ... the center of the second electrode 13 ... the third electrode,
14 ... Fourth electrode,
15 ... fifth electrode,
16 ... Sixth electrode,
17 ... seventh electrode,
18 ... 8th electrode,
19 ... ninth electrode,
310 ... 10th electrode 311 ... 11th electrode 20 ... 2nd board | substrate,
20a ... the second main surface,
20u ... second substrate part,
30 ... Liquid crystal layer,
31, 32 ... refractive index distribution,
77 ... Control unit 80 ... Display element 87 ... Display drive unit 101, 102, 103, 104 ... Liquid crystal optical element 111, 112, 113, 114 ... Liquid crystal optical device 211, 212, 213, 214 ... Image display device

Claims (8)

A first substrate having a main surface;
A second substrate;
A liquid crystal layer provided between the main surface of the first substrate and the second substrate;
A plurality of first electrodes provided between the main surface of the first substrate and the liquid crystal layer and arranged in a first direction parallel to the main surface;
A central portion provided between the main surface of the one substrate and the liquid crystal layer, disposed between the plurality of first electrodes, each provided between a pair of end portions and the pair of end portions. A plurality of second electrodes,
A plurality of pairs of third electrodes provided between the second substrate and the liquid crystal layer;
A plurality of pairs of fourth electrodes provided between the second substrate and the liquid crystal layer and aligned with the plurality of pairs of third electrodes in the first direction;
An optical element comprising:
A first voltage is applied to the plurality of first electrodes, a second voltage is applied to the plurality of second electrodes, a third voltage is applied to the plurality of pairs of third electrodes, and the plurality of pairs of fourth electrodes A control unit for applying a fourth voltage to
With
The pair of third electrodes is provided between the pair of fourth electrodes,
When the fourth electrode is projected onto the main surface, the fourth electrode overlaps a first midpoint of the width of the first electrode in the first direction;
When the plurality of second electrodes and the plurality of pairs of third electrodes are projected onto the main surface, each of the pair of third electrodes overlaps each of the pair of end portions of the one second electrode,
The first voltage V1, the second voltage V2, the third voltage V3, and the fourth voltage V4 are:
A gradient index liquid crystal optical device having the relationship The length along the first direction of the gap between the first electrode and the second electrode closest to the first electrode is equal to or less than the thickness of the liquid crystal layer in the second direction perpendicular to the main surface. The gradient index liquid crystal optical device according to claim 1. 3. The gradient index liquid crystal optical device according to claim 1, wherein a width of the second electrode along the first direction is equal to or greater than a thickness of the liquid crystal layer in a second direction perpendicular to the main surface. . The first voltage is greater than the second voltage, and the third voltage is greater than or equal to the first voltage;
The gradient index liquid crystal optical device according to any one of claims 1 to 3. A fifth electrode provided between the second substrate and the liquid crystal layer, and provided between the third electrode and the fourth electrode;
The second midpoint of the line segment along the first direction connecting the first electrode and the second electrode is located in the gap between the third electrode and the fifth electrode projected onto the main surface. ,
The gradient index liquid crystal optical device according to claim 1. The controller applies a fifth voltage to the fifth electrode;
The first voltage V1, the second voltage V2, the third voltage V3, and the fifth voltage V5 are:
And
The gradient index liquid crystal optical device according to claim 5, satisfying the relationship: The controller applies a fifth voltage to the fifth electrode;
The first voltage V1, the second voltage V2, the third voltage V3, and the fifth voltage V5 are:
The gradient index liquid crystal optical device according to claim 5 or 6. A gradient index optical device according to any one of claims 1 to 7,
A display element;
An image display device comprising: